1. Field of the Invention
This invention relates to power source switch circuit and more particularly to a power source switch circuit wherein, in a television set or the like, when only a main switch for feeding a power source voltage to the entire set is operated, a sub-switch for feeding the power source voltage to the respective circuits will be able to be automatically switched on.
2. Description of the Related Art
Conventionally, in most television sets or the like, there are provided a switch (mentioned as a sub-switch hereinafter) for feeding an electric power to respective circuits within the set and a main switch for feeding an electric power from a commercial alternating current power source to the entire set.
In such television set or the like, while the main switch is engaged, the sub-switch will be able to be controlled by the operation of a remote control or the like so that the power source of the television circuit may be switched on/off.
FIG. 3 is a block diagram showing a conventional power source switch circuit which is of an all-off type wherein, when a main switch 2 is switched off, all the power feeds will be eliminated.
A commercial alternating current power source (AC) not illustrated is fed to an AC plug 1. One input terminal of a first power source circuit 3 is connected to one power source line of the AC plug 1 through the main switch 2. Further, one input terminal of a second power source circuit 5 is connected to the above mentioned one power source line of the AC plug 1 through the main switch 2 and a sub-switch 4. The other input terminal of the first power source circuit 3 and the other input terminal of the second power source circuit 5 are connected to the other power source line of the AC plug 1. One output terminal of the second power source circuit 5 is connected to a television signal circuit not illustrated and the other output terminal is connected to a reference potential point.
There are three output terminals in the first power source circuit 3. The first output voltage is fed as a driving voltage Ss to a microcomputer 9, the second output voltage is fed as a resetting signal Sr to the microcomputer 9 and the third output voltage is fed to one end of a relay winding 4c of the sub-switch 4. The other end of the relay winding 4c is connected to a reference potential point through a collector-emitter path of a transistor 7. One end and the other end of the relay winding 4c are connected with each other through a surge absorbing diode 6. A relay controlling signal Sd from the microcomputer 9 is fed to the base of the transistor 7 through a resistance R1.
An operating circuit 8 for the user to switch on/off the power source of the television set with a remote control or the like or to operate the channel and a memorizing apparatus 10 provided with a non-volatile memory memorizing last channel positions, power source data or the like are connected to the microcomputer 9.
As described above, the present power source data of the sub-switch 4 are stored in the memorizing apparatus 10 so that, in case the main switch 2 is once switched off and is then again switched on, these power source data will be read out of the memorizing apparatus 10 by the microcomputer 9 to reproduce the last switching on/off of the sub-switch 4. That is to say, if the sub-switch 4 is on last, the microcomputer 9 will output an on-signal as a controlling signal Sd but, if the sub-switch 4 is off last, the microcomputer 9 will operate to output an off-signal as a controlling signal Sd.
Now, it shall be considered that the power source data stored in the memorizing apparatus 10 are stored as switched on and the main switch 2 is engaged.
When the main switch 2 is engaged, the first power source circuit 3 will be first switched on and the driving voltage Ss and resetting signal Sr will be fed to the microcomputer 9. The microcomputer 9 will be switched on by the driving voltage Ss and will be initially set by the resetting signal Sr and the initially set microcomputer 9 will read out the last power source data stored as switched on in the memorizing apparatus 10, will output a high level signal as a controlling signal Sd and will feed it to the base of the transistor 7 through the resistance R1 to switch on the transistor 7.
When the transistor 7 is switched on, an electric power will be fed to the relay winding 4c of the sub-switch 4 from the output terminal of the first power source circuit 3 and the relay winding 4c will be excited. The contacts 4a and 4b will contact with each other and, the commercial alternating current power source will be fed to the second power source circuit 5 and will be switched on. When the second power source circuit 5 is switched on, a predetermined electric power will be fed to the respective circuits of the television set not illustrated.
Now, it shall be considered that the power source data stored in the memorizing apparatus 10 are stored as switched off and the main switch 2 is engaged.
When the main switch 2 is engaged, the first power source circuit 3 will be first switched on and the driving voltage Ss and resetting signal Sr will be fed to the microcomputer 9. The microcomputer 9 will be switched on by the driving voltage Ss and will be initially set by the resetting signal Sr.
The initially set microcomputer 9 will read out the last power source data stored as switched off in the memorizing apparatus 10, will output a low level signal as a controlling signal Sd, will feed it to the base of the transistor 7 through the resistance R1 and the transistor 7 will not be switched on. As the transistor 7 is not switched on, the sub-switch 4 will remain off, the second power source circuit 5 will not be switched on and no electric power will be fed to the respective circuits of the television set.
However, as seen from the user side, there has been a problem that, though it is expected that, when the main switch 2 is engaged, the sub-switch 4 will be switched on, depending on the contents of the power source data stored in the memorizing apparatus 10, the television set will not operate to be switched on.
On the other hand, if the sub-switch 4 is controlled to be always switched on when the main switch 2 is engaged, the above mentioned problem will be solved. However, if it is thus controlled, in case the electricity is interrupted while the main switch 2 is engaged as it is (on stand-by), then the electricity is restored and the commercial alternating current power source is again fed to the first power source circuit 3, the sub-switch 4 will be freely switched on, though the stand-by should be restored, the electric power will be fed to the respective circuits of the television set and no favorable result will be made.
FIG. 4 is a block diagram of another conventional example. The components and parts corresponding to those in FIG. 3 shall bear the same reference numerals.
In FIG. 4, the difference from the conventional example in FIG. 3 is that the driving voltage Ss output from the first power source circuit 3 is fed not only to the microcomputer 9 but also to a detecting switch 11 so that the driving voltage Ss may be fed as a detecting signal Sk to the microcomputer 9 through the detecting switch 11. The other formations than this are the same as in the conventional example in FIG. 3.
In FIG. 4, the detecting switch 11 is an unlocked type switch which will be interlocked to be momentarily on and then off in case the main switch 2 is engaged. When this detecting switch 11 is switched on, the driving voltage Ss from the first power source circuit 3 will be led as a detecting signal Sk into the microcomputer 9 through the detecting switch 11. When the microcomputer 9 reads out this detecting signal Sk, the sub-switch 4 will be able to be controlled to be on.
Now, it shall be considered that the main switch 2 is engaged.
When the main switch 2 is engaged, the first power source circuit 3 will be first switched on and the driving voltage Ss will be fed to the microcomputer 9 and one end of the detecting switch 11. At the same time, the resetting signal Sr will be fed to the microcomputer 9 from the first power source circuit 3. The microcomputer 9 will be switched on by the driving voltage Ss and will be initially set by the resetting signal Sr. At the same time when the main switch 2 is engaged, the detecting switch 11 will be momentarily switched on and the driving voltage Ss fed to the detecting switch 11 will be led as a detecting signal Sk into the microcomputer 9 through the detecting switch 11.
When the microcomputer 9 receives the detecting signal Sk, the microcomputer 9 will enter a controlling operation of switching on the sub-switch 4 irrespective of the contents of the power source data stored in the memorizing apparatus 10, will output a high level signal as a controlling signal Sd and will feed it to the base of the transistor 7 through the resistance R1 to switch on the transistor 7.
When the transistor 7 is switched on, an electric power will be fed to the relay winding 4c of the sub-switch 4 from the output terminal of the first power source circuit 3 and the relay winding 4c will be excited. The contacts 4a and 4b will contact with each other, the commercial alternating current power source will be fed to the second power source 5 and the second power source circuit 5 will be switched on. When the second power source circuit 5 is switched on, the electric power will be fed to the respective circuits of the television set.
Next, it shall be considered that electricity is interrupted while the main switch 2 is engaged as it is and the sub-switch 4 is off (on stand-by) and is then restored and the commercial alternating current power source is again fed to the first power source circuit 3.
When the commercial alternating current power source is again fed to the first power source circuit 3 while the main switch 2 is engaged as it is, the first power source circuit 3 will be switched on and the driving voltage Ss will be fed to the microcomputer 9 and one end of the detecting switch 11. At the same time, the resetting signal Sr from the first power source circuit 3 will be fed to the microcomputer 9. The microcomputer 9 will be switched on by the driving voltage Ss and will be initially set by the resetting signal Sr. As the main switch 2 is not engaged now, the detecting switch 11 will not be switched on and the detecting signal Sk will not be fed to the microcomputer 9.
As the detecting signal Sk is not fed and the memorized data (off-data of the sub-switch 4) of the memorizing apparatus 10 are off, the initially set microcomputer 9 will not enter the operation of controlling switching on the sub-switch 4, will output a low level signal as a controlling signal Sd and will feed it to the base of the transistor 7 through the resistance R1. Therefore, the transistor 7 will not be switched on. As the transistor 7 is not switched on, the sub-switch 4 will remain switched off, the second power source circuit 5 will not be switched on and no electric power will be fed to the respective circuits of the television set. Thereby, the miss-operation after the electricity is restored can be prevented.
However, in order to meet the above mentioned operation, a very high mechanical precision will be required of the operation of the main switch 2 and detecting switch 11. Further, depending on the timing until the microcomputer 9 is started by the first power source circuit 3 and the timing of switching the detecting switch 11 on and then off, for example, when the main switch 2 is switched on and the driving voltage Ss is fed to the microcomputer 9 from the first power source circuit 3, in case the detecting switch 11 is already off at this time, the detecting signal Sk from the detecting switch 11 will not be fed to the microcomputer 9 and the above mentioned expected effect will not be able to be obtained.
FIG. 5 is a block diagram showing another conventional example. The components and parts corresponding to those in FIG. 4 shall bear the same reference numerals.
In FIG. 5, the difference from the conventional example in FIG. 4 is that a time constant circuit comprising a resistance R2 and condenser 12 is inserted between the detecting switch 11 and microcomputer 9 so that the detecting signal Sk from the detecting switch 11 momentarily switched on may be held for a fixed time in the condenser 12. The other formations than this are the same as in the conventional example in FIG. 4.
Now, it shall be considered that the main switch 2 is engaged.
When the main switch 2 is engaged, the first power source circuit 3 will be first switched on and the driving voltage Ss will be fed to the microcomputer 2 and one end of the detecting switch 11. At the same time, a resetting signal Sr will be fed to the microcomputer 9 from the first power source circuit 3. The microcomputer 9 will be switched on by the driving voltage Ss and will be initially set by the resetting signal Sr. At the same time when the main switch 2 is engaged, the detecting switch 11 will be momentarily switched on, the driving voltage Ss fed to the detecting switch 11 will become a detecting signal Sk through the detecting switch 11 and the detecting signal Sk will be fed to the condenser 12 through the resistance R2.
Thereby, even in case the detecting switch 11 is switched off before the microcomputer 9 rises, the detecting signal Sk charged by the condenser 12 will be fed to the microcomputer 9, therefore, the same as in the conventional example in FIG. 4, the microcomputer 9 will operate to control switching on the sub-switch 4 and will be able to feed a predetermined electric power to the respective circuits of the television set from the second power source circuit 5.
However, in order to meet the above mentioned operation, yet a very high mechanical precision will be required of the operation of the main switch 2 and detecting switch 11. Further, depending on the timing until the microcomputer 9 is started by the first power source circuit 3 and the timing of switching the detecting switch 11 on and then off, for example, before the main switch 2 is switched on and the driving voltage Ss is output from the first power source circuit 3, if the detecting switch 11 is already switched off, the condenser 12 will not be charged by detected information and the above mentioned expected effect will not be able to be obtained.
As described above, in the conventional power source switch circuit in FIG. 3, there has been a disadvantage that, even if the main switch is engaged, as the sub-switch is controlled on the basis of the power source data (the last on/off state of the sub-switch) stored in the memorizing apparatus, depending on the contents of the power source data, the sub-switch will not be able to be positively switched on and the electric power will not be able to be fed to the respective circuits of the television set.
The other conventional examples than are shown in FIGS. 4 and 5 are considered to be adopted but to have respectively the above described defects and are not yet practiced.